The present invention pertains to ground control to satellite communication and more particularly to a digital ranging turn-around transponder arrangement.
Tracking, telemetry and control transponder on satellites receive signals from ground stations and may pass through (turn-around) these signals and re-transmit them to the earth station which originally sent the signals. By the re-transmission of a signal from the earth station to a satellite back to the earth station, information regarding the satellite's orbit may be determined by the earth station.
Typical tracking, telemetry and control transponders are implemented with analog technology and require that the transponder demodulate a phase modulated ranging signal. The phase modulated ranging signal is extracted from the carrier signal, filtered, re-modulated and re-transmitted to the earth station. Analog phase detectors, filters and modulator are typically employed to perform these functions.
As more of the satellite's circuitry has become digital it has become inefficient and costly to continue the implementation of the ranging functions in analog circuitry.
Accordingly, it is an advantage of the present invention to provide improved tracking, telemetry and control transponder performance by minimizing the delay variation of the transmitted signals between the earth station and the transponder of the satellite.